When flying an aircraft, a pilot will typically make an elevator trim adjustment to compensate for longitudinal pitching moments that act on the aircraft independently of the pilot control of the elevator. A principal cause of such pitching moments is a difference in the center of gravity of the aircraft and its aerodynamic center. The center of gravity of an aircraft changes as fuel and ordinance are consumed, or as the distribution of mass on or within the aircraft changes during a flight. The aerodynamic center changes if the flight control configuration of the aircraft is altered, for example, as a result of extending the flaps, or lowering the landing gear.
While the elevator trim adjustment is not essential, since the pilot can control the elevator to maintain a setting that compensates for pitching moments, it is generally preferable that the pilot employ this adjustment. In many aircraft designs, the elevator trim adjustment does not reduce the range of elevator control available to the pilot. Thus, in such aircraft, a pilot will want to properly set the trim adjustment, rather than simply manually control the elevator to compensate for the longitudinal pitching moments acting on the aircraft, so that the pilot retains the full range of elevator control.
Microsoft Corporation has developed a software program entitled, “Combat Flight Simulator 3: Battle for Europe™” that is designed to run on a conventional personal computer. Tihs program enables a user to fly various combat aircraft in a computer simulation in which the user may engage in “dogfights” with other aircraft or fly bombing and other types of combat missions. Most users of the program find that the task of simply controlling a simulated aircraft in combat requires most of their effort and concentration. The simulation is intentionally designed to be as realistic as possible, and flight controls on the simulated aircraft closely emulate those on a real aircraft. The simulated combat aircraft include virtually all of the flight controls that are provided on an actual aircraft of the same type, including an elevator trim control, if such a control is included on the actual aircraft of that type. However, since many users of the combat flight simulation program are not experienced pilots, such users may find it difficult to attend to less critical details of flying an aircraft, such as adjusting the elevator trim control. This control should be adjusted periodically as changes occur in the center of gravity or in the aerodynamic center of an aircraft during a mission. While an experienced pilot would have little problem in manually adjusting the elevator trim control as needed, most novice users of the program will not understand the proper operation of the trim control or will find that attention to such details are just too much of a distraction from the more pressing aspects of flying an aircraft and avoiding being shot down. Thus, it would be desirable to make the task of simulated flying “easier” for less experienced users by providing an automated adjustment of the elevator pitch trim control, so that the user can attend to more critical functions required for flying the aircraft. Provision of such an automated “control assistant” should preserve the realism of the simulated flying experience, while freeing a user from actually making this less critical flight control adjustment. It would also be desirable to enable a user who has become more expert or is already experienced to selectively turn off the automatic adjustment and instead, manually adjust the longitudinal pitch trim control. Clearly, use of an automatic pitch trim control is not limited to a combat flight simulation program, but instead, is also applicable to other kinds of flight simulation programs in which inexperienced users attempt to fly simulated aircraft.